I decided to research this issue more carefully.
OP's link with its title:
China Releases its First Roadmap for Space Science and Exploration Through 2050. - Universe Today
China plans to send taikonauts, its astronauts, to the Moon by 2030, and to Mars by 2033, and to eventually build long-term bases on both places.
Landing taikonauts on the Moon? That seems feasible, because return of astronauts from the Moon's surface was successfully demonstrated a half century ago. Landing taikonauts on Mars? That does not have anything comparable for Mars's surface. To date, no spacecraft has attempted to depart that planet's surface for an orbit around that planet. I've seen a plausible compromise: go into orbit around Mars.
A minimum-energy trajectory has 9 months to Mars, a year at Mars, then 9 months back from Mars, giving a total of 2 1/2 years.
China Maps Out Plans to Put Astronauts on the Moon and on Mars - The New York Times
About going to Mars and then returning,
“Technically, it is feasible in theory, but it has huge challenges in engineering because the scale is very large, we have estimated at least 900 days of travel” based on current technologies, Mr. Zhou said.
That's about right for a minimum-energy trajectory.
With nuclear propulsion, the trip could be trimmed to 500 days, he said, without predicting whether China would adopt that approach.
Nuclear-reactor rocket engines? There are two main types: thermal and electric.
Thermal ones have been researched for years:
NERVA and
NASA, DARPA Will Test Nuclear Engine for Future Mars Missions - NASA -- but no nuclear-thermal rocket engine has ever been tested in flight. Such engines have a further problem: they require liquid hydrogen as a propellant, to get high exhaust velocities. Anything else has a big problem: nuclear reactors with them will be *worse* than chemical engines. That is because nuclear reactors' heat is made in their fuel rods, heat which then will be conducted to the propellant. So the temperature cannot be great enough to soften or melt the reactor's internal structure. That limit is currently around 950 C, though very refractory reactor materials may enable higher temperatures. Chemical engines, however, can easily have exhaust much hotter than their engine structures, something done routinely. Many common ones get up to 3,300 C or thereabouts.
This is from v(exh) ~ sqrt(k*T/m)
for Boltzmann's constant k, temperature T, and molecular weight m.
Hydrogen is at about 2 atomic mass units, water is at 18 amu, CO2 at 44 amu, etc. So to get v(exh) up, one needs to get m down, and the best way to do that is with hydrogen. Everything else does at least 3 times worse. H2 has the problem of being very cryogenic, with a boiling point of about 20 K or -253 C. Oxygen is also cryogenic, though not as much, with a boiling point of 90 K or -183 C.
The other type, nuclear-electric, involves a nuclear reactor powering an electric engine. But successfully-flown electric engines have low thrust, in the 100-millinewton range. There's a technology being researched called
Variable Specific Impulse Magnetoplasma Rocket (VASIMR), but it has never been flown, only demonstrated in labs.
Huang Weifen, chief designer of China’s astronaut program, said she was looking at ways to make sure that astronauts could stay healthy for a 500-day trip.
“It is another qualitative leap in flying — a very big challenge for people in terms of the medical issues, the psychological issues and living guarantees,” she said.
